I deleted my duplicates after approximately House of Wolves with the exception of maybe Ghorn. It's funny how we get attached to things like that. The bigger vault problem was my collection of armor sets for all three characters. Again though, it seems kinda childish, given that I only used one set for the majority of all my game play. The only thing I would change out was the exotic pieces depending on the circumstances. I don't have any inventory issues in D2 though - mostly because of lackluster exotics and ugly armor.